Phosphor and manufacturing method for the same, and light source

ABSTRACT

To provide a phosphor having an emission characteristic such that a peak wavelength of light emission is in a range from 580 to 680 nm, and having a high emission intensity, and having a flat excitation band with high efficiency for excitation light in a broad wavelength range from ultraviolet to visible light (wavelength range from 250 nm to 550 nm). For example, Ca 3 N 2 (2N), AlN(3N), Si 3 N 4 (3N), Eu 2 O 3 (3N) are prepared, and after weighing and mixing a predetermined amount of each raw material, raw materials are fired at 1500° C. for 6 hours, thus obtaining the phosphor including a product phase expressed by a composition formula CaAlSiN 3 :Eu and having an X-ray diffraction pattern satisfying a predetermined pattern.

This is a Division of application Ser. No. 12/285,295 filed Oct. 1,2008, which is a Division of application Ser. No. 11/182,190 filed Jul.15, 2005, now U.S. Pat. No. 7,476,337, which claims priority to JP2004-220630 filed Jul. 28, 2004 and JP 2005-207215 filed Jul. 15, 2005.The entire disclosures of the prior applications are hereby incorporatedby reference herein.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a phosphor used in a display devicesuch as a cathode-ray tube (CRT), a plasma display (PDP), a fieldemission display (FED), electroluminescence (EL) display, a fluorescentdisplay tube, and an illumination device such as a fluorescent lamp, anda manufacturing method of the same, and alight source using thephosphor.

BACKGROUND ART

At present, a discharge type fluorescent lamp and an incandescent bulbused as the illumination device involve problems that a harmfulsubstance such as mercury is contained, and life span is short. However,in recent years, a high luminescence LED emitting light of nearultraviolet/ultraviolet to blue color has been developed in sequence,and the white LED illumination for the practical application of the nextgeneration has been actively studied and developed, by combining thelight of ultraviolet to blue color generated from the LED, and aphosphor having an excitation band in a range from ultraviolet to bluecolor. When the white LED illumination is put to practical use, sinceefficiency of converting electric energy into light is improved, lessheat is generated and it is constituted of a semiconductor device andthe phosphor, the white LED has advantages of good life span withoutburn-out of a filament as is seen in a conventional incandescent bulb,being strong against vibration and repeated on/off operation, and havingno harmful substance such as mercury contained therein, thus realizingan ideal illumination device. Further, by utilizing the aforementionedcharacteristic, the aforementioned white LED is noted as a backlight fora liquid crystal display which replaces a CCFL (cold-cathode tube) otherthan as illumination.

Here, in order to obtain a white light by combining the aforementionedLED and the phosphor, generally two systems are considered. In one ofsuch systems, white light emission is obtained by combining a blue lightemitting LED and a yellow light emitting phosphor (such as YAG:Ce) whichemits yellow color by receiving and excited by the blue light emission,and by a principle of mixed state of lights of blue light emission andyellow light emission.

In another system, the white light emission is obtained, by combining anear ultraviolet/ultraviolet light emitting LED, a red (R) lightemitting phosphor by receiving and excited by the nearultraviolet/ultraviolet light emission, a green (G) light emittingphosphor, a blue (B) light emitting phosphor, and others, and using amixed state of the lights of the R, G, B and others emitted from thephosphor. A method of obtaining the white light emission by the lightsof the R, G, B and others has wide applications, because an arbitrarylight emission color other than the white light can be obtaineddepending on a combination and a mixing ratio of each phosphor of the R,G, B and others. As the phosphors used in the aforementioned usage,examples are given such as Y₂O₂S:Eu, La₂O₂S:Eu, 3.5MgO.0.5MgF₂.GeO₂:Mn,(La, Mn, Sm)₂O₂S.Ga₂O₃:Eu as the red phosphor, ZnS:Cu, Al, SrAl₂O₄:Eu,BAM:Eu, Mn as the green phosphor, and BAM:Eu, Sr₅(PO₄)₃Cl:Eu, ZnS:Ag,Cl, (Sr, Ca, Ba, mg)₁₀(PO₄)₆Cl:Eu as the blue phosphor. Then, bycombining the phosphors of the R, G, B, and others with a light emittingpart such as the near ultraviolet/ultraviolet light emitting LED, alight source and an illumination device such as an LED emitting whitelight or the light with desired emission color can be obtained.

However, in the white LED illumination obtained by combining the blueLED and the yellow phosphor (YAG:Ce), the light emission on the longerwavelength side of a visible light becomes insufficient, thus emittingthe light with slightly bluish white emission color, and the white lightemission with slightly reddish white color like an electric bulb can notbe obtained.

In addition, in the white LED illumination obtained by combining thenear ultraviolet/ultraviolet LED and the phosphor of R, G, B, andothers, the red phosphor out of three color phosphors has a deterioratedexcitation efficiency, thereby exhibiting low emission efficiency,compared to other phosphors. Therefore, the mixing ratio of only redphosphor must be increased and the phosphor for improving luminancebecomes thereby insufficient, making it impossible to obtain white colorwith high luminance. Further, a problem involved therein is that theaforementioned red phosphor has a sharp emission spectrum, therebyexhibiting deteriorated color rendering property.

Further, from the viewpoint of improving the emission efficiency of thelight emitting element and the phosphor, in the case of theaforementioned YAG:Ce yellow phosphor, the YAG:Ce yellow phosphor is inan excitation range with high efficiency when it is caused to emit lightby using blue light emitted from the blue LED, whereby an excellentyellow light emission can be obtained. However, when it is caused toemit light by using the near ultraviolet/ultraviolet light emitted fromthe near ultraviolet/ultraviolet LED, the YAG:Ce yellow phosphor is outof the excitation range with high efficiency, and therefore an adequatelight emission can not be obtained. This means that the excitation rangewith high efficiency is narrow for the YAG:Ce yellow phosphor.

Then, the problem that the excitation range with high efficiency isnarrow for the YAG:Ce yellow phosphor involves a situation such that awavelength balance of blue color and yellow color is lost, because theemission wavelength of the blue LED is out of an optimal excitationrange of the YAG:Ce yellow phosphor by the deviation of an emissionwavelength caused by the deviation of the light emitting elements duringmanufacturing the blue LED even in a case of light emission by using theblue light emitted from the aforementioned blue LED. When theaforementioned situation occurs, the problem involved therein is that acolor tone of the white light which is obtained by synthesizing the bluelight and the yellow light is changed. Here, in manufacturing the LED,it is difficult to prevent the deviation of the light emitting elementsin the present circumstances. Therefore, in order to prevent the changeof the color tone, the phosphor having characteristics of a broad andflat excitation band is desired.

Therefore, recently, an oxynitride glass phosphor having an excellentexcitation band on the longer wavelength side and capable of obtainingan emission peak with a broad half value width (for example, see patentdocument 1), and a sialon-based phosphor (for example see patentdocuments 2 and 3), and a silicon nitride-based phosphor containingnitrogen (for example, see patent documents 4 and 5) are reported. Then,the phosphor containing the nitrogen has a larger ratio of covalent bondthan an oxide phosphor, and therefore has an excellent excitation bandin the light with the wavelength of 400 nm or more, gathering attentionas a white LED phosphor. However, such a phosphor fails in reaching asatisfactory level in the present circumstances.

(Patent document 1) Japanese Patent Laid Open No. 2001-214162(Patent document 2) Japanese Patent Laid Open No. 2003-336059(Patent document 3) Japanese Patent Laid Open No. 2003-124527(Patent document 4) Japanese Patent Laid Open No. 2003-515655(Patent document 5) Japanese Patent Laid Open No. 2003-277746

SUMMARY OF THE INVENTION

In view of the above-described circumstances, the present invention isprovided, and an object of the present invention is to provide aphosphor having an emission characteristic of having an emissionspectrum with a peak in a wavelength range from 580 to 680 nm with ahigh emission intensity, and an excitation band characteristic of havinga flat excitation band with high efficiency for excitation light in abroad wavelength range from ultraviolet to visible light (wavelengthrange from 250 to 550 nm) and a manufacturing method of the same, and alight source using the phosphor.

In order to solve the aforementioned problem, the inventors of thepresent invention prepares a plurality of phosphor samples. Then, in aprocess of firing a raw material of the phosphor sample, the phosphorsample according to the present invention satisfying the aforementionedemission characteristic and excitation band characteristic is found fromfired phosphor samples, with an atmosphere gas ventilated in a firingfurnace during firing. Then, a crystal structure of the phosphoraccording to the present invention is identified by using an X-raydiffraction method. Specifically, the X-ray diffraction pattern of thephosphor according to the present invention and a JCPDS (Joint Committeeon Power Diffraction Standards) card are compared, and the crystalstructure of the phosphor according to the present invention isidentified. As a result, a known crystal structure is found which isconsidered to be similar to the phosphor according to the presentinvention. However, the crystal structure having an identical crystalface interval is not found. Therefore, it is found that the phosphoraccording to the present invention has a new crystal structure. Then,the inventors of the preset invention define the phosphor according tothe present invention, with the X-ray diffraction pattern shown by thephosphor according to the present invention. (the X-ray diffractionpattern in the present invention is used in the same meaning as an X-raydiffraction spectrum and an X-ray diffraction chart.)

Specifically, the present invention takes several aspects as follows.

In a first aspect, a phosphor is provided, comprising a phase showing adiffraction peak with relative intensity of 10% or more in the Braggangle (2θ) range from 36.5° to 37.5° and from 41.9° to 42.9° of theX-ray diffraction pattern as a main product phase, when the relativeintensity of the diffraction peak having a highest intensity in a powderX-ray diffraction pattern by CoKα ray is defined as 100%.

In a second aspect, a phosphor is provided, comprising a phase showing adiffraction peak with relative intensity of 10% or more in the Braggangle (2θ) range from 36.5° to 37.5° and from 41.9° to 42.9°, and from56.3° to 57.3° of the X-ray diffraction pattern, when the relativeintensity of the diffraction peak having a highest intensity in a powderX-ray diffraction pattern by CoKα ray is defined as 100%.

In a third aspect, a phosphor is provided, comprising a phase showing adiffraction peak with relative intensity of 10% or more in the Braggangle (2θ) range from 36.5° to 37.5° and from 40.9° to 41.9°, 41.9° to42.9°, 56.3° to 57.3°, 66.0° to 67.0°, 75.8° to 76.8°, and 81.0° to83.0° of the X-ray diffraction pattern, when the relative intensity ofthe diffraction peak having a highest intensity in a powder X-raydiffraction pattern by CoKα ray is defined as 100%.

In a fourth aspect, the phosphor according to any one of the first tothird aspects is provided, wherein a crystal system of the product phaseis an orthorhombic system.

In a fifth aspect, the phosphor according to any one of the first tofourth aspects is provided, wherein the product phase is expressed by acomposition formula MmAaDbOoNn:Z, where element M is at least one ormore kind of element having bivalent valency, element A is at least oneor more kind of element having tervalent valency, element D is at leastone or more kind of element selected from the elements havingtetravalent valency, O is oxygen, N is nitrogen, and element Z is atleast one or more kind of element selected from rare earth elements ortransitional metal elements, satisfying n=2/3 m+a+4/3b−2/3o, m/(a+b)1/2, (o+n)/(a+b)>4/3, o≧0, and m:a:b=1:1:1.

In a sixth aspect, the phosphor according to any one of the first tofourth aspects is provided, wherein the product phase is expressed by acomposition formula MmAaDbNn:Z, where element M is at least one or morekind of element having bivalent valency, element A is at least one ormore kind of element having tervalent valency, element D is at least oneor more kind of element selected from the elements having tetravalentvalency, N is nitrogen, and element Z is at least one or more kind ofelement selected from rare earth elements or transitional metalelements, satisfying m:a:b:n=1:1:1:3.

In a seventh aspect, the phosphor according to either of the fifthaspect or the sixth aspect is provided, wherein the element M is atleast one or more kind of element selected from the group consisting ofMg, Ca, Sr, Ba, and Zn, and the element A is Al, the element D is Si,and the element Z is at least one or more kind of element selected fromEu, Mn, and Ce.

In an eighth aspect, the phosphor according to any one of the fifth toseventh aspects is provided, wherein the element M is Ca, the element Ais Al, the element D is Si, and the element Z is Eu.

In a ninth aspect, the phosphor according to any one of the first toeighth aspects is provided, wherein no diffraction peak with relativeintensity of beyond 5% exists in the Bragg angle (2θ) range from 38.0°to 40.0° of the X-ray diffraction pattern, when the powder X-raydiffraction pattern of the phosphor by CoKα ray is measured, and therelative intensity of the diffraction peak with highest intensity in theX-ray diffraction pattern is defined as 100%.

In a tenth aspect, the phosphor according to any one of the fifth toninth aspects is provided, wherein a wavelength of a maximum peak in anemission spectrum is 650 nm or more, when the phosphor is irradiatedwith more than one kind of monochromatic lights in a wavelength rangefrom 250 nm to 550 nm or continuous light including this wavelengthrange as an excitation light.

In an eleventh aspect, the phosphor according to any one of the fifth totenth aspects is provided, wherein the size (Dx) of a crystallite of thephosphor particle is 50 nm or more.

In a twelfth aspect, the phosphor according to any one of the fifth toeleventh aspects is provided, wherein a unit volume of a crystal latticeof the product phase included in the phosphor is 275 Å³ or more.

In a thirteenth aspect, the phosphor according to any one of the fifthto twelfth aspects is provided, wherein a lattice constant of thecrystal lattice of the product phase included in the phosphor is a=9.75Å or more, b=5.64 Å or more, and c=5.05 Å or more.

In a fourteenth aspect, a manufacturing method of the phosphor accordingto any one of the first to thirteenth aspects is provided, comprisingthe steps of:

obtaining a mixture by weighing and mixing raw material powders of thephosphor;

obtaining a fired material by firing the mixture in a firing furnace;and

obtaining the phosphor by pulverizing the fired material,

wherein in the step of obtaining the fired material by firing themixture, any one of the gases such as nitrogen, ammonia, mixed gas ofthe ammonia and the nitrogen, or mixed gas of the nitrogen and hydrogenis used as an atmosphere gas during firing.

In a fifteenth aspect, the manufacturing method of the phosphoraccording to the fourteenth aspect is provided, wherein the gascontaining 80% or more of nitrogen gas is used as the atmosphere gas inthe firing furnace during firing.

In a sixteenth aspect, the manufacturing method of the phosphoraccording to either of the fourteenth or fifteenth aspect is provided,wherein in the step of obtaining the fired material by firing themixture in the firing furnace, the mixture is fired, while 0.01 L/min ormore of atmosphere gas is ventilated in the firing furnace duringfiring.

In a seventeenth aspect, the manufacturing method of the phosphoraccording to any one of the fourteenth to sixteenth aspects is provided,wherein in the step of obtaining the fired material by firing themixture in the firing furnace, the pressure of atmosphere gas is set at0.001 MPa or more and 0.1 MPa or less to make the inside the firingfurnace in a pressurized state.

In an eighteenth aspect, a light source is provided, using the phosphoraccording to any one of the first to thirteenth aspects.

The phosphor according to the first to thirteenth aspects of the presentinvention has the excellent emission characteristic of having theemission spectrum with a peak in the wavelength range from 580 to 680 nmand particularly having a high emission intensity with a peak in thelonger wavelength side, e.g. at 650 nm or more, and further has theexcitation band characteristic of having a flat excitation band withhigh efficiency in a broad wavelength range from ultraviolet to visiblelight (wavelength range from 250 to 550 nm).

According to the manufacturing method of the phosphor described in anyone of the fourteenth to seventeenth aspects, the oxygen in the phosphorcomposition described in any one of the first to thirteenth aspects isreduced, and the phosphor having an emission spectrum with a peak on thelonger wavelength side and having an improved emission efficiency can beeasily manufactured at an inexpensive manufacturing cost.

According to a light emission apparatus described in the eighteenthaspect, the light emission apparatus having a desired emission color,having a high emission intensity and luminance, and having highefficiency can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a powder X-ray diffraction pattern of a main product phase ofa phosphor according to the present invention, and the comparison ofpeaks between the measured X-ray diffraction pattern and a JCPDS card.

FIG. 2 is a graph showing an excitation spectrum of the main productphase of the phosphor according to the present invention.

FIG. 3 is a graph showing an emission spectrum of the main product phaseof the phosphor according to the present invention.

FIG. 4A is a powder X-ray diffraction pattern of the main product phaseof the phosphor according to the examples 2 to 4 of the presentinvention.

FIG. 4B is an expanded view of the powder X-ray diffraction pattern ofthe main product phase of the phosphor according to the examples 2 to 4of the present invention.

FIG. 4C is an expanded view of the powder X-ray diffraction pattern ofthe main product phase of the phosphor according to the examples 2 to 4of the present invention.

FIG. 4D is an expanded view of the powder X-ray diffraction pattern ofthe main product phase of the phosphor according to the examples 2 to 4of the present invention.

FIG. 4E is an expanded view of the powder X-ray diffraction pattern ofthe main product phase of the phosphor according to the examples 2 to 4of the present invention.

FIG. 4F is an expanded view of the powder X-ray diffraction pattern ofthe main product phase of the phosphor according to the examples 2 to 4of the present invention.

FIG. 4G is an expanded view of the powder X-ray diffraction pattern ofthe main product phase of the phosphor according to the examples 2 to 4of the present invention.

FIG. 5 is the X-ray diffraction pattern of the conventional phosphoraccording to a comparative example.

FIG. 6 is the X-ray diffraction pattern of the conventional phosphoraccording to a comparative example.

FIG. 7 is the powder X-ray diffraction pattern of the main product phaseof the phosphor according to the examples 7 and 8 of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

The phosphor according to the present invention provides the phosphorincluding a product phase expressed by a composition formula such asMmAaDbOoNn:Z (in some cases, simply described as “product phase”hereunder.). Here, element M is at least one or more kind of elementselected from the elements having bivalent valency in a main productphase of the phosphor, element A is at least one or more kind of elementhaving tervalent valency in the product phase, element D is at least oneor more kind of element having tetravalent valency in the product phase,O is oxygen, N is nitrogen, and element Z is the element acting as theactivator in the product phase and is one or more kind of elementselected from rare earth elements or transitional metal elements. Whenthe product phase has a crystal structure defined by an X-raydiffraction pattern as will be described later, the product phaseexhibits an excellent emission characteristic having the emissionspectrum with a peak in a wavelength range from 580 to 680 nm and havinga high emission intensity, and further exhibits an excitation bandcharacteristic having a flat excitation band with high efficiency in abroad wavelength range from ultraviolet to visible light (wavelengthrange from 250 to 550 nm).

Further, when the product phase has a chemically stable composition, animpurity phase not contributing to light emission is hardly generated inthe composition, and therefore the deterioration in the emissioncharacteristic can be suppressed, to thereby realize a preferablestructure. Therefore, in order to have the chemically stablecomposition, preferably, the product phase has the composition expressedby the aforementioned composition formula MmAaDbOoNn:Z satisfying n=2/3m+a+4/3b−2/3o, m/(a+b)≧1/2, (o+n)/(a+b)>4/3, o≧0. However, any one ofthe m, a, and b is not 0.

Further, in the product phase having the aforementioned compositionformula MmAaDbOoNn:Z, the element M is the element having +bivalentvalency, the element A is the element having +tervalent valency, theelement D is the element having +tetravalent valency, the oxygen is theelement having−bivalent valency, the nitrogen is the elementhaving−tervalent valency. Therefore, when the m, a, b, o, and n have thecomposition satisfying n=2/3m+a+4/3b−2/3o, the valency of each elementis added to become zero, and preferably, the composition of the productphase becomes further stable compound. Further, in the case of o=0,satisfying m:a:b:n=1:1:1:3, the phosphor having excellent emissioncharacteristic and excitation band characteristic is obtained. In anycase, a slight deviation of the composition from the composition formulashowing the composition of the product phase is allowable.

However, in some cases, the phosphor manufactured to satisfy o=0,andm:a:b:n=1:1:1:3 includes the aforementioned product phase and aslight amount of oxygen. It is considered that the oxygen thus slightlycontained is the oxygen initially contained in the raw material, theoxygen mixed in by oxidization of the surface of the material when thematerial is weighed, mixed, and fired, and further the oxygen adsorbedon the surface of the phosphor after firing. When judging from ananalysis result of the phosphor according to the examples as will bedescribed later, less content of the oxygen in the phosphor ispreferable from the viewpoint of the emission efficiency, and preferablythe content of the oxygen to the mass of the product phase is 5.0 wt %or less, further preferably is 3 wt % or less.

In addition, when the aforementioned product phase is expressed byMmAaDbOoNn:Zz, preferably an amount of the element Z to be added isdetermined, so that the molar ratio z/(m+z) of the element M to theactivator element Z is in the range of not less than 0.0001 and not morethan 0.50. When the molar ratio z/(m+z) of the element M to the elementZ is in the above-described range, deterioration in the emissionefficiency can be averted, which is caused by concentration quenchingdue to excessive content of the activator (element Z). Meanwhile, thedeterioration in the emission efficiency can also be averted, which iscaused by insufficient emission contributing element due to inadequatecontent of the activator (element Z). Further, more preferably, thevalue of the z/(m+z) is in the range of not less than 0.0005 and notmore than 0.1. However, an optimal value of the range of the value ofthe z/(m+z) is slightly fluctuated according to the kind of theactivator (element Z) and the kind of the element M. Further, bycontrolling the amount of the activator (element Z) to be added also,the peak wavelength of the light emission of the product phase can beset so as to be shifted, and this is effective when adjusting theluminance in the light source.

Meanwhile, in the product phase having the aforementioned compositionformula MmAaDbOoNn:Z, the crystal structure of the product phase ischanged by controlling the molar ratio o of the oxygen, and the peakwavelength of the light emission wavelength of the phosphor can besifted in the range from 600 nm to 660 nm. However, in the case ofm=a=b=1, as the concentration of the oxygen is thus increased, the lightemission characteristic of the phosphor is deteriorated. Therefore, themolar ratio o of the oxygen is preferably controlled in the range of0≦o≦m When the oxygen content is in the range of 0≦o≦m, the generationof impurity composition can be suppressed, and the deterioration of theemission intensity of the product phase can be prevented. Furtherpreferably, when the oxygen content to the mass of the product phase is3 wt % or less and in the range of 0≦o≦0.1, the position of a main peakin the X-ray diffraction pattern as will be described later is preventedfrom deviating from a preferable range of the Bragg angle (2θ), and thephosphor can exhibit a sufficient emission intensity.

When the phosphor of the present invention is manufactured as the rawmaterial of the element M (+bivalent valency), the element A (+tervalentvalency), the element D (+tetravalent valency), any compound of eachnitride and oxide may be used. For example, the raw materials may bemixed by using the nitride (M₃N₂), oxide (MO) of the element M, and thenitride (AN, D₃N₄) of the element A and D. Then, by controlling theblending ratio of both of the nitride and the oxide, an amount of theoxygen and an amount of the nitrogen in the phosphor can be controlled,without changing the value of m. As a matter of course, the meaning ofthe nitride and the oxide is not limited to the compound obtained bycombining with only oxygen, or combining with only nitrogen. Forexample, the compound here is obtained when carbonate and oxalate aredecomposed during firing, to become substantially oxide, resulting inhaving the aforementioned elements and the oxygen. In the case of thenitrogen also, the compound has the aforementioned elements and thenitrogen. However, for simplifying the explanation, the oxide of theaforementioned elements, and the nitride of the aforementioned elementsare explained as the compound having the aforementioned elements and theoxygen and as the compound having the aforementioned elements and thenitrogen, respectively.

For example, when the raw materials are weighed, under the condition ofthe oxygen molar ratio o=0, and m=a=b=1, each raw material may beweighed with the molar ratio of M₃N₂:AN:D₃N₄=1:3:1. Further, at thistime, when the activator element Z is the element having bivalentvalency, the element Z replaces a part of the element M. Therefore, whensuch a replacement is taken into consideration and the product phase isexpressed by MmAaDbNn:Zz, preferably (m+z)=a=b=1 is established. Thus,the composition of the product phase can have a chemically stablecomposition. Also, when the raw materials are weighed under thecondition of the oxygen molar ratio o=0.25 and m=a=b=1, each rawmaterial may be weighed with the molar ratio ofM₃N₂:MO:AN:D₃N₄=0.75:0.75:3:1.

The element M is preferably at least one or more kind of elementselected from the group consisting of Be, Mg, Ca, Sr, Ba, Zn, Cd, andHg, further preferably is at least one or more kind of element selectedfrom the group consisting of Mg, Ca, Sr, Ba, and Zn.

The element A is preferably at least one or more kind of elementselected from the element having tervalent valency such as B (boron),Al, Ga, In, Tl, Y, Sc, P, As, Sb, and Bi, and further preferably is oneor more kind of element selected from the group consisting of B, Al, andGa, and most preferably is Al. As the Al, preferably AlN is used as ageneral thermoelectric material and structural material, is easilyavailable at a low cost, and in addition, has a small environmentalload.

The element D is preferably at least one or more kind of elementselected from the group consisting of C, Si, Ge, Sn, Ti, Hf, Mo, W, Cr,Pb, and Zr, is further preferably the elements Si and/or Ge, and is mostpreferably the element Si. As the Si, preferably Si₃N₄, which isnitride, is used as the general thermoelectric material and structuralmaterial, is easily available at a low cost, and in addition has a smallenvironmental load.

The element Z is preferably one or more kind of element selected fromthe rare earth elements or the transitional metal elements. From theviewpoint of exhibiting a sufficient color rendering properties by eachkind of white light source such as the white LED lighting unit using thephosphor of the present invention, preferably the light emission of theproduct phase has the spectrum with a broad half value width. Inaddition, from the same viewpoint, preferably the element Z is one ormore kind of element selected from the group consisting of Eu, Mn, Sm,and Ce. Among these elements, when Eu is used as the element Z, theproduct phase has the emission spectrum with a half value width of 50 nmor more in the range from orange color to red color, exhibiting a stronglight emission with high emission efficiency. Therefore, this ispreferable as the activator of each kind of light source such as a whitelight illumination and a white LED. In addition, the phosphor having thelight emission with different wavelengths can be obtained, in accordancewith the kind of the element Z which replaces a part of the element M inthe composition of the product phase.

Particularly, when the light emission apparatus with excellent colorrendering properties is manufactured by using the aforementionedphosphor, preferably the peak wavelength of the emission wavelength ofthe phosphor is set at 650 nm or more, and further preferably is set at6565 mm or more. Here, as a general manufacturing method of thephosphor, the concentration of the activator element Z (here, theelement Z is Eu, and is referred to as Eu in some cases hereafter) isincreased, whereby the emission wavelength can be shifted toward thelonger wavelength side. However, a phenomenon of concentration quenchingoccurs, such that the emission efficiency is deteriorated when theconcentration of Eu is excessively increased. Therefore, the inventorsof the present invention study on shifting of the emission wavelengthfurther to the longer wavelength side without excessively increasing thecontent of Eu. As a result, although as will be described in detail, astructure is realized, in which the emission wavelength is efficientlyshifted to the longer wavelength side by controlling a unit lattice ofthe crystal structure included in the phosphor.

As a result, the peak wavelength of the phosphor can be set at 650 nm ormore without decreasing the emission efficiency, and chromaticity pointsof the light emission of the phosphor is substantially 0.65 or more onthe x-axis, and 0.35 or less on the y-axis on the CIE chromaticitycoordinates. Therefore, the emission spectrum of the phosphor takes thecoordinates infinitely close to red color of the right end on the CIEchromaticity coordinates, and color reproducibility of the red color isimproved as the light emission apparatus. In addition, when the lightsource emitting white light is manufactured by combining the phosphor ofthis invention and other phosphor, the mixing ratio of a red phosphorcan be reduced, compared to the case of manufacturing the white light ofthe same color temperature by using the conventional red phosphor (forexample, comparative example 1).

Particularly, in the white LED illumination obtained by combining theblue LED and the yellow phosphor (YAG:Ce), when the correlated colortemperature of the light emission apparatus is set in the range from7000K to 2500K by mixing with the phosphor of the present invention, thelight emission apparatus exhibiting a significantly preferable colorrendering properties is obtained, having 80 or more of average colorrendering index Ra, and further preferably having 80 or more of R15 and60 or more of R9. Further, when the color rendering property describedabove is exhibited, the mixing amount of the phosphor according to thepresent invention may be 20% or less of the yellow phosphor (YAG:Ce),and in this case, the light emission apparatus with excellent colorrendering properties having 80 or more of Ra can be obtained withoutreducing the emission efficiency of the yellow phosphor.

When the phosphor of the present invention is used in a powdery shape,the average particle size of the phosphor powder is preferably 20 μm orless. This is because the light emission appears to occur mainly on thesurface of the particle in the phosphor powder, and therefore when theaverage particle size (note that the average particle size of thepresent invention refers to a median size (D50).) is 20 μm or less, thesurface area per unit weight of the powder can be secured, and thedeterioration in luminance can be prevented. Further, when the powder isformed in a pasty state and is applied to a light emitting element orthe like also, the density of the powder can be increased. From thisviewpoint also, the deterioration in luminance can be prevented. Inaddition, according to the study of the inventors of the presentinvention, although detailed reason is unknown, from the viewpoint ofthe emission efficiency of the phosphor powder, it was found thatpreferably the average particle size was larger than 0.1 μm. Asdescribed above, the average particle size of the phosphor powder of thepresent invention is preferably 0.1 μm or more and 20 μm or less, andfurther preferably 3.0 μm or more and 15 μm or less. The averageparticle size (D50) specified here is the value measured by an LS230(laser diffraction scattering method) manufactured by Beckman CoulterInc. Also, from the aforementioned viewpoints, the value of the specificsurface area (BET) of the phosphor powder of the present invention is0.05 m²/g or more and 5.00 m²/g or less.

Next, a powder X-ray diffraction pattern shown by the phosphor of thepresent invention will be explained with reference to FIGS. 1A and 1B.

FIG. 1A is the powder X-ray diffraction pattern by CoKα ray of thephosphor according to an example 1 as will be described later as anexample of the phosphor according to the present invention, and FIG. 1Bis a comparative result of peaks between the X-ray diffraction patternand a JCPDS card. Here, peak data that occupies an upper half portion ofFIG. 1B shows the Bragg angle (2θ) and intensity of a main peak shown inFIG. 1A by the position and height of a line segment. Next, the cardpeak that occupies a lower half portion shows the Bragg angle (2θ) andintensity of a main peak of CaAlSiN₃ (39-0747) crystal described in theJCPDS card by the position and height of the line segment. (However, forsimplifying the comparison between both peaks, the JCPDS card peakintensity of CaAlSiN₃ crystal is described by turning upside down.)

As clearly shown from the comparison between the both peaks shown inFIG. 1B, overall patterns of the main peaks of the phosphor of thepresent invention and the CaAlSiN₃ crystal described in the JCPDS cardare similar. However, if the both peaks are observed in detail, any peakof the phosphor of the present invention is Lifted toward a smallerBragg angle (2θ), and although there is a similarity between eachcrystal structure, these crystal structures have different crystal faceintervals. The difference between both crystal structures is possiblycaused as follows. Nitride raw materials such as Ca₃N₂, MN, and Si₃N₄are used totally in the element forming a matrix structure of thephosphor according to the present invention, while CaO, AlN, and Si₃N₄are used as the raw materials in the CaAlSiN₃ described in the JCPDScard. Therefore, there is a difference in the amount of the oxygenpresent in both crystal structures, and a part of Ca is replaced with Euin the case of the phosphor according to the present invention. However,the overall patterns of the main peaks are similar, and therefore itappears that the product phase of the phosphor according to the presentinvention also has an orthorhombic crystal system similar to theCaAlSiN₃ crystal described in the JCPDS card.

As described above, the inventors of the present invention consider thatalthough the product phase of the phosphor of the present invention hasthe crystal system similar to the CaAlSiN₃ crystal described in theJCPDS card, the phosphor according to the present invention has a newcrystal structure having different crystal face intervals. Therefore,the structure of the phosphor according to the present invention havingthe new crystal structure is defined by the X-ray diffraction patternshown by the phosphor.

Here, the main peak in the X-ray diffraction pattern of the productphase included in the phosphor of the present invention will beexplained.

As clearly shown in FIG. 1A, the product phase included in the phosphoraccording to the present invention had characteristic peaks in the Braggangle (2θ) range from 36.5° to 37.5°, 40.9° to 41.9°, 41.9° to 42.9°,56.3° to 57.3°, 66.0° to 67.0°, 75.8° to 76.8°, and 81.0° to 83.0°, andamong these ranges, the peak in the range from 36.5° to 37.5°, and 41.9°to 42.9° had a high intensity and particularly characteristic, followedby the characteristic peak in the range from 56.3° to 57.3°, and any ofthese peaks was a diffraction peak having 10% or more of relativeintensity, when the relative intensity of the diffraction peak havingthe highest intensity in the X-ray diffraction pattern was defined as100%. All of the characteristic diffraction peaks show that the crystalphase having a large crystal face interval than the CaAlSiN₃ crystaldescribed in the aforementioned JCPDS card is generated as a singlephase.

Further, if these peaks are observed from the viewpoint of the halfvalue width of the diffraction pattern, the half value widths of thesediffraction peaks are all 0.25° or less. These sharp diffraction peaksshow that the product phase has not an amorphous structure but astructure excellent in crystallinity.

The relation between the aforementioned X-ray diffraction pattern, andthe excellent emission characteristic and the excellent excitation bandcharacteristic shown by the phosphor of the present invention has notbeen clarified yet, but is considered as follows.

First, it appears that there is a close relation between the fact thatthe X-ray diffraction pattern shows a peak pattern wherein a targetproduct phase is obtained by a single phase, and the fact that thephosphor of the present invention has the excellent emissioncharacteristic and the excellent excitation band characteristic. Whenthe target product phase is thus obtained by a single phase, as aresult, the peaks of the raw materials (Ca₃N₂, AlN, Si₃N₄, and Eu₂O₃)used for manufacturing the phosphor are not observed in the X-raydiffraction pattern. Specifically, during manufacturing the phosphor, inthe case of an inadequate firing temperature and improper mixing amountof the raw materials, the raw materials excessively exists other thanthe target product phase, thereby reducing the amount of the phosphorper unit area irradiated with excitation light, and the raw materialsthus excessively exist absorb the excitation light and emitted light,whereby the emission efficiency of the phosphor is deteriorated and theexcellent emission characteristic can not be obtained. Accordingly, whenthere is no peak observed in the raw material in X-ray diffractionpattern, it appears that the phosphor to be measured has the excellentemission characteristic and the excellent excitation band.

Further, it appears that a high intensity of the X-ray diffraction peakreflects a high crystallinity of the product phase. When the lightemission easily occurs around Eu²⁺ in the product phase because of ahigher crystallinity of the product phase and this structure furthercontinues regularly, the excellent emission characteristic is obtained.Meanwhile, when the X-ray diffraction peak intensity is weak and thecrystallinity is considered to be low, an order of the structure aroundthe Eu²⁺ serving as the center of the light emission is insufficient.Therefore, a distance between each Eu²⁺ ions becomes too close, tothereby cause the concentration quenching and the situation that theEu²⁺ does not enter the site where the Eu²⁺ must enter. Therefore, theexcellent emission characteristic can not be obtained.

Finally, the inventors of the present invention found that the relativeintensity of the peak observed near the Bragg angle (2θ) range from 38.0to 40.0° was weak and further preferably no diffraction peak wasobserved in both ranges from 38.5 to 39.5° and 44.0 to 45.0°, and thisreflects the fact that the excellent emission characteristic and theexcellent excitation band characteristic can be obtained. This isbecause the peak observed near the Bragg angle (2θ) range from 38.0 to40.0° is considered to the peak of AlN which is the raw material of thephosphor. Namely, as described above, during manufacturing the phosphor,in the case of the inadequate firing temperature and improper mixingamount of the raw materials, residual raw material exists in thephosphor after firing, having harmful effects on the emissioncharacteristic or the like. Among the residual raw materials, if AlNremains, the residual AlN absorbs the emitted light and the excitationlight of a phosphor sample because the AlN is gray, thereby directlyleading to the deterioration of the emission intensity. Therefore, inorder to obtain the phosphor with high emission intensity, a weakerdiffraction peak intensity of the AlN near the range from 38.0 to 40.0°is preferable. Specifically, when the powder X-ray diffraction patternby CoKα ray is measured and the relative intensity of the diffractionpeak with highest intensity in the X-ray diffraction pattern is definedas 100%, it is preferable to allow no diffraction peak with the relativeintensity of beyond 5% to exist. Further preferably, absolutely nodiffraction peak (considered to be the diffraction peak of AlN) isobserved in both ranges from 38.5 to 39.5° and 44.0 to 45.0°.

Here, explanation will be given to a measuring method of the powderX-ray diffraction pattern of the phosphor according to the presentinvention.

The phosphor to be measured was pulverized up to a predetermined averageparticle size (preferably 1.0 μm to 20.0 μm) by using pulverizing meanssuch as the mortar and the ball mill after firing, and a holder made oftitanium was filled with the phosphor thus pulverized to form a flatsurface, then the phosphor was measured by an XRD apparatus, “RINT 2000”by RIGAKU DENKI CO., LTD. Measurement conditions are described below.

-   -   Used measuring apparatus: “RINT 2000” by RIGAKU DENNKI CO., LTD.    -   X-ray tube bulb: CoKα    -   Tube voltage: 40 kV    -   Tube current: 30 mA    -   Scanning method: 2θ/θ    -   Scanning speed: 0.3°/min    -   Sampling interval: 0.01°    -   Start angle (2θ): 10°    -   Stop angle (2θ): 90°

It appears that the deviation of the Bragg angle (2θ) is generated byfactors such as an unflat sample face irradiated with X-ray, ameasurement condition of the X-ray, and particularly difference in thescanning speed. Therefore, it appears that a slight deviation isallowable in the range where the aforementioned characteristicdiffraction peak is observed. In this specification, in order torestrain such a deviation, the scanning speed is set at 0.3°/min, and inthis condition, Si is mixed in the phosphor sample, and the deviation ofSi peak is corrected after X-ray measurement, to thereby determine theBragg angle (2θ).

Further, a crystal structure analysis of the phosphor sample wasconducted by the inventors of the present invention by using a Rietveldmethod, based on the powder X-ray measurement result, in associationwith the measurement of a peak position of the XRD. By the Rietveldmethod, more accurate model of the crystal structure is guided by makingvarious kinds of structural parameters more precise by a least squaremethod in the model of the latter diffraction intensity of the X-ray, soas to make the difference small between a X-ray pattern obtained from anactual measurement and a X-ray pattern obtained from the theoreticalcalculation using a model of the estimated crystal structure. A program“RIETAN-2000” was used for a Rietveld analysis and the crystal structureof the CaAlSiN₃ described in the JCPDS card 30-0747 was used.

As a result of the analysis of the crystal structure by the Rietveldmethod, as shown in table 1, the lattice constant of the a-axis, b-axis,and c-axis in the crystal lattice of the phosphor sample was increased,in association with improvement of the emission characteristic of thephosphor sample, and along with this, the increase in volume of thecrystal lattice was also observed. The volume is thus increased at arate proportional to the decrease of the amount of the oxygen containedin the phosphor sample, and by such a decrease of the amount of theoxygen, the volume of the crystal lattice is increased. A detailedreason of this phenomenon is unknown. However, when the oxygen enters aCaAlSiN₃ lattice which constitutes the phosphor sample, the oxygenreplaces the nitrogen in the lattice. Here, the lattice volume of theimpurity phase which is generated by mixing-in of the oxygen is mailerthan the lattice volume of the chase having ro oxygen mixed-in.Therefore, it is considered that when the ratio of the impurity phase islarge, the lattice volume of the phosphor sample in total becomes small.Accordingly, when the lattice constant and the lattice volume becomelarge, the size of crystallites becomes large by decreasing of the ratioof the impurity phase, and this reveals that purer phase is generated.

As a result of inspecting the relation between the emissioncharacteristic of the phosphor and the amount of the oxygen containedtherein as an impurity by using various phosphor samples, it was foundthat in order to obtain the phosphor having 650 nm or more of emissionpeak wavelength, the amount of the oxygen contained as the impurity waspreferably 3.0 wt % or less, and the lattice constant of each crystallattice was a=9.75 Å or more, b=5.64 Å or more, c=5.05 Å or more, andthe volume of the crystal lattice was 275.0 Å³ or more, and furtherpreferably a=9.80 Å or more, b=5.65 Å or more, c=5.06 Å or more and thevolume of the crystal lattice was 280.5 Å³. (In this invention, thea-axis, b-axis, and c-axis are shown in the order of the lengthsatisfying a>b>c. The same thing can be said even if the order of the a,b, c is replaced with each other depending on determining the atomiccoordinates.)

In addition, the relation between the emission characteristic of thephosphor and a crystallite size was inspected by using theaforementioned phosphor sample. Here, the crystallite size was obtainedby the method described hereunder.

First, a half value width B was calculated for a plurality ofdiffraction peaks of the diffraction pattern obtained by the powderX-ray diffraction measurement of the phosphor sample according to thepresent invention. Then, by using a Sherrer's formula Dx=0.9λ/Bcosθ(wherein, Dx is the size of a crystallite, λ, is the wavelength of X-rayused for measurement, B is the half value width of the diffraction peak,and θ is the Bragg angle of the diffraction peak), an averaged size (Dx)of the crystallite was obtained from the diffraction peak in the Braggangle (2θ) range from 36.5° to 37.5°, 41.9° to 42.9°, and 56.3° to57.3°. Then, it is reveled that the larger the size of the crystallite,the more improved in the crystallinity of a phosphor particle thusmanufactured, and the improvement of the emission efficiency can beestimated. As a result of inspecting the relation between the emissioncharacteristic of the phosphor and the crystallite size, by usingvarious kinds of phosphor samples, it was found that in order to obtainthe phosphor having 650 nm or more of emission peak wavelength, it wasfound that the crystallite size was 20 nm or more, more preferably was50 nm or more, and further preferably 90 nm or more.

As described above, the inventors of the present invention achieves thecrystal structure, the lattice constant, and the crystallite sizecontributing to the improvement of the emission characteristic of thephosphor sample by using the Rietveld method and the Sheller formula,and an importance of controlling the oxygen concentration in thephosphor sample for controlling the crystal structure, the latticeconstant, and the crystallite size. Therefore, after further studying,the inventors of the present invention achieves the manufacturing methodof the phosphor capable of controlling the oxygen concentration in thephosphor sample, and explanation will be given thereto hereunder.

First, in the manufacture of the phosphor, as a source of mixing-in ofthe oxygen in the step before firing, the oxygen contained in the rawmaterials and the oxygen adhered to the crucible or the like areconsidered. Therefore, it is important to reduce the amount of theoxygen thus mixed-in. However, it is difficult to remove all of theoxygen thus mixed-in. Here, the inventors of the present inventionachieves the structure wherein the oxygen is removed in the step offiring in the phosphor manufacture, by making an atmosphere gas in afiring furnace reductive atmosphere at high temperature, to therebydecompose and nitride the raw material.

Further, as a result of studying on a reduction method of the amount ofthe oxygen remaining in the phosphor after firing, the inventors of thepresent invention achieved the possibility that the oxygen contained inEu₂O₃, as the raw material was released by the high temperaturereductive atmosphere and recombined to a crystalline phase of thephosphor generated during firing. Therefore, the inventors of thepresent invention achieved also the structure wherein in the firing stepof the phosphor, the atmosphere gas was ventilated in the firingfurnace, thereby controlling the ventilation flow rate to carry away theoxygen thus released from the sample to the outside the firing furnace.

Specifically, the atmosphere gas was continuously flown/exhausted in orout of the firing furnace. In this condition, the effect of reducing theamount of the oxygen in the sample was confirmed at 0.01 L/min or moreof the ventilation amount, and a remarkable effect was confirmed withthe increase of the ventilation amount. Accordingly, from the viewpointof improving the emission characteristic of the phosphor, preferably theatmosphere gas to be introduced in the furnace is preferably ventilatedat 0.01 L/min or more from the initial period of firing, and furtherpreferably ventilated at 1.0 L/min or more.

Meanwhile, the pressure of the firing furnace in a firing step in thephosphor manufacture is preferably set in a pressurized state so thatthe oxygen in an atmosphere is not mixed in the furnace. However, whenthe pressure is beyond 0.1 MPa, a special pressure withstanding designis required in a design of a furnace installation. Therefore, preferablythe pressure is 0.1 MPa or less in view of a productivity. In addition,when the pressure is increased, sintering between phosphor particlesprogresses excessively, thus making it difficult to pulverize afterfiring. Therefore, the pressure is preferably set at 0.001 MPa or more,and 0.05 MPa or less.

The atmosphere gas to be ventilated in the firing furnace is not limitedto nitrogen, but any one of the ammonia, the mixed gas of the ammoniaand the nitrogen, or the mixed gas of the nitrogen and the hydrogen maybe used. However, as described above, when the oxygen is contained inthe atmosphere gas, an oxidizing reaction of the phosphor particleoccurs. Therefore, it is preferable to have the oxygen contained in theatmosphere gas as impurity, as little as possible, and preferably 100ppm or less oxygen is contained therein. Further, when moisture iscontained in the atmosphere gas, in the same way as the oxygen, theoxidizing reaction of the phosphor occurs during firing. Therefore, itis preferable to have the moisture contained as impurity, as little aspossible, and preferably 100 ppm or less moisture is contained therein.Here, when a single gas is used as the atmosphere gas, a nitrogen gas ispreferable. Although firing by using ammonia gas independently may bepossible, the ammonia gas is increased in a cost and is corrosive gas.Therefore, a special treatment is required for an apparatus and anexhausting method at a low temperature. Accordingly, when the ammonia isused, lower concentration of the ammonia is preferable by mixing withthe nitrogen. For example, when the mixed gas of the nitrogen gas andthe ammonia is used, preferably the nitrogen is set at 80% or more, andthe ammonia is set at 20% or less. Also, when the mixed gas of thenitrogen and other gas is used, nitrogen partial pressure is decreasedin the atmosphere gas when gas concentration other than the nitrogen isincreased. Therefore, from the viewpoint of accelerating a nitridingreaction of the phosphor, inert or reductive gas containing 80% or moreof nitrogen is preferably used.

Next, the manufacture of Ca_(0.985)AlSiN₃:Eu_(0.0150) will be explainedas an example of the manufacturing method of the phosphor according tothe present invention.

Each nitride raw material of the element M, the element A, and theelement D may be a commercially available raw material. However, higherpurity is preferable and the raw material with 2N or more, furtherpreferably with 3N or more is therefore prepared. Preferably, theparticle diameter of each particle of the raw material is generally afine particle from the viewpoint of accelerating reaction. However, theparticle size and the shape of the phosphor obtained are changedaccording to the particle size and the shape of the raw material.Therefore, by adjusting to the particle diameter required for thephosphor finally obtained, the nitride raw material and the oxide rawmaterial having the particle approximating to the particle size of thephosphor thus obtained, may be prepared.

In regards to the raw material, from the viewpoint of the productivityof the phosphor, the average particle size of each raw material ispreferably set at 0.1 μm or more, and 5.0 μm or less. Of course,preferably all the raw materials have the average particle size of 0.1μm or more and 5.0 μm or less. However, by using the raw material havingthe aforementioned average particle size for AlN and Si₃N₄, which arethe raw materials of the element forming a matrix structure havinghigher melting points, the phosphor having an excellent emissioncharacteristic can be manufactured.

As the raw material of the element Z, the commercially available rawmaterial such as nitride or oxide raw material, is preferable. Ofcourse, higher purity of each raw material is preferable, and the rawmaterial with 2N or more, further preferably with 3N or more istherefore prepared. Note that the oxygen contained in the oxide rawmaterial of the element Z is slightly supplied in the composition of theproduct phase. Therefore, it is preferable to take an oxygen supplyamount into consideration, when studying on blending the aforementionedelement M raw material, element A raw material, and element D rawmaterial. When the oxygen is contained as little as possible in thecomposition of the product phase, a simple substance of the element Z orthe nitride of the element Z may be used as the raw material. However,as described above, by ventilating the atmosphere gas in the firingfurnace, the amount of the oxygen in the composition can be reducedduring firing. Therefore, preferably the oxide of the element Z which iseasily available at a low cost on manufacturing may be used.

When manufacturing Ca_(0.985)AlSiN₃:Eu_(0.0150), Ca₃N₂(2N), AlN(3N),Si₃N₄(3N) may be prepared respectively as the nitride of the element M,the element A, and the element D, for example. Eu₂O₃(3N) is prepared asthe element Z.

These raw materials are weighed and mixed to become 0.985/3 mol ofCa₃N₂, 1.0 mol of AlN, 1/3 mol of Si₃N₄, and 0.015/2 mol of Eu₂O₃, sothat the molar ratio of each element becomesCa:Al:Si:Eu=0.985:1:1:0.015.

The nitride of each raw material element is easily influenced by oxygenand humidity, and therefore it is preferable to operate the weighing andmixing in a glove box under an inert atmosphere. The inert gas used asan atmosphere may be used, from which the oxygen and the humidity issufficiently removed. When the nitride raw material is used as each rawmaterial element, a dry mixing system is preferable as a mixing systemto avoid the decomposition of the raw material. A usual dry mixingmethod using a ball mill and a mortar may be used.

The raw material thus mixed is put in a crucible, retained and fired inthe inert atmosphere such as nitrogen at not less than 1000° C.,preferably at not less than 1400° C., and more preferably at not lessthan 1500° C. and not more than 1600° C. for 30 minutes or more. Notethat higher firing temperature allows the solid-phase reaction toprogress rapidly, thereby shortening a retaining time. However,excessively higher firing temperature allows the sintering betweenparticles to become violent, thereby progressing aparticle growth,whereby a coarse particle is generated and an evaporation or reductionof the raw material occurs. Therefore, preferably the firing temperatureis set at 1600° C. or less. Meanwhile, even when the firing temperatureis low, a target emission characteristic can be obtained by maintainingthe aforementioned temperature for a long time. In addition, longersintering allows a particle growth to progress, thereby enlarging aparticle shape. Therefore, the sintering time may be set in accordancewith a target particle size.

Note that as described above, when the atmosphere gas is continuouslyventilated in the firing furnace during firing, the effect of reducingthe amount of the oxygen in a phosphor crystal is confirmed at 0.01L/min or more of the ventilation amount, and the effect becomesremarkable with the increase of the ventilation amount. Accordingly,preferably 0.01 L/min or more of the atmosphere gas to be introduced inthe furnace is ventilated from the initial period of firing, and furtherpreferably 1.0 L/min or more of the atmosphere gas is ventilated.

Further, when the crucible formed of BN (boron nitride) is used as acrucible, preferably the mixing-in of the impurities from the cruciblecan be prevented. After completing the firing, the fired material istaken out from the crucible, and is pulverized up to a predeterminedaverage particle size by using pulverizing means such as a mortar and aball mill, whereby the phosphor containing the product phase expressedby the composition formula Ca_(0.985)AlSiN₃:Eu_(0.015) can bemanufactured.

Even when other element is used as the element M, the element A, theelement D, and the element Z, and an activating amount of an activatorEu is changed, the phosphor containing the product phase having apredetermined composition formula can be manufactured by the samemanufacturing method as described above, by adjusting the blendingamount of each raw material during mixing to a predetermined compositionratio.

As described above, the phosphor according to the present invention hasan excellent excitation band in a broad range from the ultraviolet tovisible light (wavelength range from 250 to 550 nm), and the emissionintensity of the aforementioned phosphor is high. Therefore, bycombining with a light emission part emitting the light of theultraviolet to blue color, the light source and the LED with high outputand further an illumination unit including such light source and LED canbe obtained.

Specifically, by combining the phosphor according to the presentinvention in a powdery state with the light emission part (particularly,the light emission part emitting the light with the wavelength rangefrom 250 nm to 550 nm) by the known method, various display device andillumination units can be manufactured. For example, by combining with adischarge lamp generating the ultraviolet light, a fluorescent lamp, theillumination unit and the display device can be manufactured, or bycombining with the LED light emitting element emitting the light of theultraviolet to blue color also, the illumination unit and the displaydevice can be manufactured. Further, by combining the phosphor of thepresent invention with an apparatus generating electron beam, thedisplay device can be manufactured.

EXAMPLES

The present invention will be specifically explained based on theexamples hereunder.

Example 1

Commercially available Ca₃N₂(3N), AlN(3N), Si₃N₄(3N), and Eu₂O₃(3N) wereprepared, and each raw material was weighed to obtain 0.985/3 mol ofCa₃N₂, 1.0 mol of AlN, 1/3 mol of Si₃N₄, and 0.015/2 mol of Eu₂O₃, andthereafter was mixed in the glove box under the nitrogen atmosphere byusing the mortar. The raw materials thus mixed were put in the crucibleand set in the firing furnace, and retained/fired for 3 hours at 1600°C. in the nitrogen atmosphere wherein the pressure is set at 0.05 MPa,with the nitrogen ventilated at 1.0 L/min while maintaining theaforementioned 0.05 MPa pressure. Thereafter, the fired object thusobtained were cooled from 1600° C. to 200° C. for 1 hour, then thephosphor including the product phase expressed by the compositionformula Ca_(0.985)AlSiN₃:Eu_(0.0150) was obtained. The particle size ofthe obtained phosphor sample was 3 to 4 μm by SEM observation.(hereafter, in the examples 2 to 6 also, the particle size of theobtained phosphor was 3 to 4 μm by SEM observation.)

The phosphor thus obtained was irradiated with the light with thewavelength of 460 nm emitted from the excitation light source, and theemission characteristic was measured. In the items of the emissioncharacteristic thus measured, the peak wavelength is the wavelengthshown by (nm) of the peak showing the wavelength with highest emissionintensity in the emission spectrum. The emission intensity shows theemission intensity in the peak wavelength with a relative intensity,with the intensity of the example 2 defined as 100%, the luminance isthe value of Y obtained based on a calculation method in the XYZ colorsystem defined in JIS Z8701, and the chromaticity x, y is obtained bythe calculation method defined in the JIS Z8701. In addition, the oxygenand nitrogen concentrations (O/N) contained in a phosphor particlesample are the values measured by using an oxygen/nitrogen simultaneousanalysis apparatus (TC-436) made by LECO INC., and other elementconcentration is the value measured by using the ICP.

A measurement result of a concentration analysis of each element, theemission characteristic, and a powder characteristic of theaforementioned phosphor is shown in table 1.

Next, a powder X-ray diffraction pattern of the aforementioned phosphorsample and the comparison result with JCPDS card are shown in FIGS. 1Aand 1B.

It is found from FIGS. 1A and 1B that the crystal structure of thephosphor according to the example 1 is similar to the CaAlSiN₃ crystaldescribed in the JCPDS card in overall patterns of the main peaks of theX-ray diffraction pattern. However, the both crystal structures areconsidered to have different crystal face intervals, due to thedifference of the amount of the oxygen which both crystal structureshave and the fact that a part of Ca is replaced with Eu. However, itappears that the product phase of the phosphor according to the presentinvention also has the orthorhombic crystal similar to the CaAlSiN₃crystal described in the JCPDS card.

In regards to the main peak in the X-ray diffraction pattern, theproduct phase included in the phosphor according to the example 1 alsohas characteristic peaks in the Bragg angle (2θ) range from 36.5° to37.5°, 40.9° to 41.9°, 41.9° to 42.9°, 56.3° to 57.3°, 66.0° to 67.0°,75.8° to 76.8°, and 81.0° to 83.0°, and among them, the peak in therange from 36.5° to 37.5°, and 41.9° to 42.9° has a high intensity andparticularly characteristic, and the peak in the range from 56.3° to57.3° is the characteristic peak that follows, and any of these peakswas a diffraction peak having 10% or more of relative intensity, whenthe relative intensity of the diffraction peak having the highestintensity in the X-ray diffraction pattern is defined as 100%.

Further, when these peaks are observed from the viewpoint of the halfvalue width of the diffraction pattern, the half value widths of thesediffraction peaks are all 0.25° or less. The aforementioned sharpdiffraction peak shows that the product phase has not an amorphousstructure but the structure excellent in crystallinity.

From the measurement result of the oxygen/nitrogen concentration, it wasfound that analytical values of the oxygen concentration and thenitrogen concentration in the phosphor sample were 2.4 wt % and 28.5 wt%, respectively. Meanwhile, the oxygen concentration and the nitrogenconcentration calculated from a raw material mixing amount of thephosphor sample were 0.3 wt % and 30 wt %, respectively.

When both concentrations are compared, in regards to the oxygenconcentration, a fair amount of oxygen is contained in the sample withrespect to 0.3 wt % oxygen concentration in the raw materials. About 2wt % of extra oxygen thus contained is considered to be the oxygeninitially adhered to the surface of the raw material, the oxygen mixedin by oxidization of the surface of the raw material during mixing andfiring, and the oxygen adsorbed on the surface of the phosphor sampleafter firing, and considered to be the oxygen that exists separatelyfrom the structure of the product phase.

Meanwhile, in regards to the nitrogen concentration, an approximatelythe same amount of nitrogen (30 wt %) as 28.5 wt % nitrogenconcentration in the product phase is contained in the sample. From thisresult, it appears that there is almost no nitrogen that existsseparately from the structure of the product phase.

Further, an excitation spectrum showing the excitation band of thephosphor sample and the emission spectrum showing the emissioncharacteristic are measured, and a result thereof is shown in FIG. 2 andFIG. 3.

FIG. 2 is a graph showing the relative intensity taken on the ordinateaxis and the excitation wavelength (nm) taken on the abscissa axis, andthe excitation spectrum of the phosphor sample is plotted by solid line.

As clearly shown from the measurement result of FIG. 2, the excitationspectrum of the phosphor sample according to the example 1 exists overthe broad range from 250 nm to 600 nm, and it was found that the lightof the broad range from the ultraviolet to visible light could besufficiently effectively utilized.

FIG. 3 is a graph showing the relative intensity taken on the ordinateaxis, and the emission wavelength (nm) taken on the abscissa axis, andthe emission spectrum of the phosphor sample is plotted by solid line.

As clearly shown from the measurement result of FIG. 3, it was foundthat the emission spectrum of the phosphor sample according to theexample 1 had a peak value at 654 nm and had the half value width overthe range of high visibility.

Example 2

The phosphor of an example 2 was obtained in the same way as the example1, excepting that the mixed raw material was put in the crucible andretained and fired for 3 hours at 1500° C. in the nitrogen atmosphere,and thereafter cooled for 1 hour from 1500° C. to 200° C., to obtain thephosphor containing the product phase expressed by the compositionformula Ca_(0.985)AlSiN₃:Eu_(0.0150).

The measurement result of the oxygen/nitrogen concentrations, theemission characteristic, and the powder characteristic of the phosphorsample are shown in table 1, and the powder X-ray diffraction pattern ofthe phosphor thus obtained is shown by thick solid line in FIGS. 4A to4G.

In FIG. 4, FIG. 4A shows the X-ray diffraction pattern over the entireBragg angle (2θ) range from 0° to 90°, and FIGS. 4B to 4G are expandedviews of characteristic parts of the Bragg angle, wherein FIG. 4B showsthe characteristic Bragg angle range from 35° to 40°, FIG. 4C shows therange from 40° to 45°, FIG. 4D shows the range from 55° to 60°, FIG. 4Eshows the range from 65° to 70°, FIG. 4F shows the range from 75° to80°, and FIG. 4G shows the range from 80° to 85°.

Example 3

In the mixing ratio of each raw material, the phosphor sample accordingto the example 3 was manufactured in the same way as the example 2,excepting that Ca₃N₂ was selected to be (0.985−0.25)/3 mol and CaO wasselected to be 0.25 mol, and the emission characteristic was measured.The measurement result of the oxygen/nitrogen concentrations, theemission characteristic, and the powder characteristic of the phosphorsample are shown in table 1, and the powder X-ray diffraction patternthus obtained is shown by thin solid line in FIGS. 4A to 4G.

Example 4

In the mixing ratio of each raw material, the phosphor sample accordingto the example 4 was manufactured in the same way as the example 2,excepting that the Ca₃N₂ was selected to be (0.985−0.50)/3 mol and theCaO was selected to be 0.50 mol, and the emission characteristic wasmeasured. The measurement result of the oxygen/nitrogen concentrations,the emission characteristic, and the powder characteristic of thephosphor sample are shown in table 1, and the powder X-ray diffractionpattern thus obtained is shown by thick solid line in FIGS. 4A to 4G.

Example 5

In the mixing ratio of each raw material, the phosphor sample accordingto the example 5 was manufactured in the same way as the example 2,excepting that the Ca₃N₂ was selected to be (0.985−0.75)/3 mol and theCaO was selected to be 0.75 mol, and the emission characteristic wasmeasured. The measurement result of the oxygen/nitrogen concentrations,the emission characteristic, and the powder characteristic of thephosphor sample are shown in table 1, and the powder X-ray diffractionpattern thus obtained is shown by thin solid line in FIGS. 4A to 4G.

Example 6

In the mixing ratio of each raw material, the phosphor sample accordingto the example 6 was manufactured in the same way as the example 2,excepting that the CaO was selected to be 0.985 mol, and the emissioncharacteristic was measured. The measurement result of theoxygen/nitrogen concentrations, the emission characteristic, and thepowder characteristic of the phosphor sample are shown in table 1, andthe powder X-ray diffraction pattern thus obtained is shown by thick onedot chain line in FIGS. 4A to 4G.

TABLE 1

CONCENTRATION PEAK EMISSION PARTICLE O N WAVELENGTH INTENSITY LUMINANCECHROMATICITY SIZE (wt %) (wt %) (nm) (%) (%) x y (μm) EXAMPLE 1 2.2 27.5656.2 115.0 104.8 0.679 0.320 4.67 EXAMPLE 2 2.4 28.5 654.0 100.0 100.00.675 0.324 4.70 EXAMPLE 3 5.2 25.1 646.1 69.7 102.6 0.649 0.350 5.04EXAMPLE 4 7.3 21.1 637.5 40.7 105.1 0.599 0.398 5.68 EXAMPLE 5 9.0 21.0624.5 30.8 102.0 0.571 0.426 7.16 EXAMPLE 6 11.3 20.7 611.0 22.4 98.40.540 0.451 9.75 EXAMPLE 7 1.9 28.0 659.0 116.5 105.2 0.683 0.317 5.34EXAMPLE 8 1.8 28.5 659.5 117.7 105.3 0.683 0.316 5.39 COMPARATIVE 3.628.1 653.8 96.4 100.0 0.674 0.325 5.20 EXAMPLE 3 PDF 39-0747 — — — — — —— — CRYSTALLITE CRYSTAL LATTICE CONSTANT DURABILITY ABSOLUTE BET SIZE(Dx) a-axis b-axis c-axis unit volume EVALUATION DENSITY (m²/g) (nm) (Å)(Å) (Å) (Å³) (%) (g/cc) EXAMPLE 1 1.10 90.8 9.806 5.653 5.066 280.8 −0.13.252 EXAMPLE 2 1.00 92.8 9.796 5.649 5.062 280.1 −1.1 3.248 EXAMPLE 30.96 68.5 9.755 5.634 5.045 277.3 −5.0 3.206 EXAMPLE 4 0.83 76.2 9.7495.599 5.030 274.6 −7.0 3.190 EXAMPLE 5 0.77 — — — — — — — EXAMPLE 6 0.63— — — — — — — EXAMPLE 7 1.01 101.9 9.806 5.655 5.067 281.0 0.0 3.241EXAMPLE 8 0.99 102.6 9.808 5.656 5.068 281.1 0.0 3.243 COMPARATIVE 1.1587.6 9.790 5.641 5.058 279.3 −2.1 3.233 EXAMPLE 3 PDF 39-0747 — — 9.5845.629 4.986 269.0 — —

indicates data missing or illegible when filed

(Study on the Examples 2 to 6)

1.) Oxygen and Nitrogen Concentrations in the Phosphor

The mixing amount of the oxygen is increased as the examples are movedfrom the examples 2 to 6, by changing the mixing ratio of the Ca₃N₂ toCaO in the raw material. Therefore, the analytical value of the oxygenconcentration in the phosphor is also increased. In addition, the oxygenconcentration in the phosphor becomes larger than the value calculatedfrom the mixing amount of the oxygen. This is because the oxygen is notonly contained in the structure of the phosphor but is present in such away that it is adsorbed on the surface or the like of the phosphorpowder, in the phosphor according to the examples 2 to 6. Meanwhile, inregards to the analytical value of the nitrogen concentration, almostthe same amount of the nitrogen as the mixing amount of the nitrogen iscontained in the sample. From this result, it is considered that almostno nitrogen is separately present from the structure of the productphase, and the nitrogen is contained in the structure of the phosphor.

2.) Relation Between the Oxygen Concentration in the Phosphor and theX-ray diffraction pattern

It was Found that the Emission Intensity of the Phosphor wasdeteriorated as the examples were moved from the examples 2 to 6. Whenthe emission intensity of the example 2 is defined as 100% as therelative intensity, the phosphor of the example 3 have about 70% of therelative intensity, while the phosphor of the examples 4 to 6 have 40%or less of the relative intensity.

Here, explanation is given to the relation between the amount of theoxygen contained in the structure of the phosphor and the X-raydiffraction pattern in the examples 2 to 6, with reference to FIG. 4A to4G. As clearly shown in FIG. 4A to 4G, it was found that the Bragg angle(2θ) having characteristic peaks in the range from 36.5° to 37.5°, 41.9°to 42.9°, 40.9° to 41.9°, 56.3° to 57.3°, 66.0° to 67.0°, 75.8° to76.8°, and 81.0° to 83.0°, was shifted toward a higher angle side, so asto close to that of the CaAlSiN₃ crystal described in the JCPDS card. Itwas found that the crystallinity was deteriorated, because the intensityof the X-ray diffraction peak was decreased in association with theincrease of the amount of the oxygen in the phosphor.

This is because the crystal structure of the phosphor is changed, by theincrease of the amount of the oxygen contained in the structure of thephosphor. Further, as is seen in the examples 4, 5, and 6, when 0.50 molor more of CaO is mixed and the mixing amount of the oxygen isincreased, the impurity phase is generated and an unreacted material isremained, to thereby possibly deteriorate the emission intensity.

Accordingly, from the viewpoint of obtaining the phosphor with highemission intensity, and when the relative intensity of the diffractionpeak with highest intensity was defined as 100% in the powder X-raydiffraction pattern by CoKα ray, it was found that the phosphors shownin the examples 2 and 3 were preferable, which have firstly the Braggangle (2θ) of the main peak with the relative intensity of 10% or morein the range from 36.5° to 37.5° and 41.9° to 42.9°, and secondarily theBragg angle (2θ) of the characteristic peak in the range from 56.3° to57.3°, and thirdly the Bragg angle (2θ) of the further characteristicpeak in the range from 40.9° to 41.9°, 66.0° to 67.0°, 75.8° to 76.8°,and 81.0° to 83.0°.

3.) Relation Between the Oxygen Concentration in the Phosphor and thePeak Wavelength of the Emission Spectrum

It was found that the peak wavelength of the emission spectrum of thephosphor was decreased from 654 nm to 611 nm, as the examples were movedfrom the example 2 to example 6.

4.) Relation Between the Oxygen Concentration in the Phosphor and theEmission Luminance

It was found that the luminance of the phosphor of each example wasapproximately constant in the examples 2 to 6. This is because thephosphor exhibits the luminance of approximately constant value by theshift of emission spectrum to a high visibility region of a human beingwhen the peak wavelength of the light emission is decreased, while theemission intensity of the phosphor is deteriorated as the examples movefrom the examples 2 to 6.

Example 7

CaAlSiN₃:Eu was manufactured in the same way as the example 1, exceptingthat the firing temperature is set at 1500° C., the firing time is setat 6 hours, and a ventilation amount of the nitrogen is set at 5.0L/min.

First, the commercially available Ca₃N₂(2N), AlN(3N), Si₃N₄(3N), andEu₂O₃(3N) were prepared. All the raw materials used at this time havethe average particle size of 5.0 μm or less. Then, each raw material wasweighed, to obtain 0.985/3 mol of Ca₃N₂, 1 mol of AlN, 1/3 mol of Si₃N₄,and 0.015/2 mol of Eu₂O₃. Next, all the raw materials were mixed byusing the mortar in the glove box under the nitrogen atmosphere, and theraw materials thus mixed were put in a BN crucible, then in the nitrogenatmosphere of 0.05 MPa pressure, retained and fired at 1500° C. for 6hours, with nitrogen ventilated therethrough at 5.0 L/min whilemaintaining the aforementioned 0.05 MPa pressure, and thereafter, thetemperature was cooled from 1500° C. to 200° C., to obtain the phosphorsample including the product phase shown by the composition formulaCa_(0.985)AlSiN₃:Eu_(0.0150) was obtained. The particle size of thephosphor sample thus obtained was 5.34 μm, and the specific surface areawas 1.01 m²/g. Further, the emission characteristic and the powdercharacteristic of the phosphor sample are shown in table 1, and thepowder X-ray diffraction pattern is shown in FIG. 7.

Example 8

The phosphor sample including the product phase shown by the compositionformula Ca_(0.985)AlSiN₃:Eu_(0.0150) was obtained in the same way as theexample 7, excepting that the ventilation amount of the nitrogen was setat 10.0 L/min. The particle size was 5.39 μm, and the specific surfacearea was 0.99 m²/g. The emission characteristic and the powdercharacteristic of the phosphor sample thus obtained, and othercharacteristics are shown in table 1, and the powder X-ray diffractionpattern is shown in FIG. 7.

(Study on the Examples 1 to 8) 1.) Control of the Oxygen Concentrationin the Sample

When the oxygen concentrations in the phosphor samples are comparedbetween the example 1 and the examples 7, 8, the oxygen concentration inthe phosphor sample manufactured in the examples 7, 8 is lower than theoxygen concentration in the sample manufactured in the example 1. Thereason is considered to be that the oxygen concentration is reduced,when the nitrogen gas is constantly ventilated in the firing furnaceduring firing the phosphor sample, thereby increasing the ventilationamount to let the oxygen in the raw material and adhered to the crucibleis released to the outside the firing furnace at initial period offiring. Further, the reason is considered to be the effect of releasingthe oxygen contained in Eu₂O₃ or the like to the outside the crystal asa sintering reaction of a phosphor raw material is progressed, and theeffect of releasing the oxygen thereafter to the outside the firingfurnace is exhibited to prevent the oxygen from recombining with thecrystal phase. A proper value of the ventilation amount of the nitrogengas during firing is considered to change depending on the volume of thefiring furnace or the shape of the furnace. However, in any case,preferably the nitrogen gas is ventilated in the furnace at 1.0 L/min ormore.

2.) Relation Between the Crystal Lattice and the Emission Characteristic

Next, based on the measurement result of the powder X-ray diffraction ofthe phosphor sample according to the examples 1 to 4 and 7, the crystalstructure analysis of the phosphor sample was performed by using theRietveld method. A program “RIETAN-2000” was used for a Rietveldanalysis, and the crystal structure of CaAlSiN₃ described in 39-0747 ofthe JCPDS card was used for the crystal structure for reference.Further, a half value width B was calculated for a plurality ofdiffraction peaks of the diffraction pattern obtained by the powderX-ray diffraction measurement of the phosphor according to the presentinvention, and from the Sheller formula Dx=0.9λ/Bcosθ (here, Dx is thesize of the crystallite, λ is the wavelength of the X-ray used formeasurement, B is the half value width of the diffraction peak, and θ isthe Bragg angle of the diffraction peak), the size of the crystallite ofthe phosphor sample was averaged and obtained from the diffraction peakin the range from 36.5° to 37.5°, and 41.9° to 42.9°, 56.3° to 57.3°,for the phosphor sample according to the example 1. The result is shownin table 1.

It was found that the phosphor sample according to the example 1 has theorthorhombic crystal structure, and the value of the a-axis was 9.806 Å,the value of the b-axis was 5.653 Å, and the value of the c-axis was5.066 Å, and a unit volume of the crystal lattice (described as acrystal lattice volume in some cases hereafter.) was 280.82 Å³. Also, itwas found that the size of the crystallite (Dx) of the phosphor samplewas 90.8 nm, e.g. not less than 50.0 nm.

It was found that the phosphor sample according to the example 2 had theorthorhombic crystal structure, and the value of the a-axis was 9.796 Å,the value of the b-axis was 5.649 Å, the value of the c-axis was 5.062Å, and the crystal lattice volume was 280.15 Å³. In addition it wasfound that the size of the crystallite (Dx) was 92.8 nm, e.g. not lessthan 50.0 nm.

In the same way, the analysis of the phosphor according to the examples3 and 4 was performed. Then, in regards to the unit lattice of thephosphor of the example 3, it was found that the value of the a-axis as9.755 Å the value of the b-axis was 5.634 Å, the value of the c-axis was5.045 Å, the crystal lattice volume was 277.26 Å³, the size of thecrystallite (Dx) was 68.5 nm. In regards to the unit lattice of thephosphor of the example 4, it was found that the value of the a-axis was9.749 Å, the value of the b-axis was 5.599 Å, the value of the c-axisvas 5.030 Å the crystal lattice volume as 274.60 Å³, and the size of thecrystallite (Dx) was 76.2 nm.

It was found that the phosphor sample according to the example 7 had theorthorhombic crystal structure, and the value of the a-axis was 9.806 Å,the value of the b-axis was 5.655 Å, the value of the c-axis was 5.067Å, the crystal lattice volume was 280.99 Å³, and the size of thecrystallite (Dx) was 101.9 nm, e.g. not less than 50.0 nm. In the sameway, it was found that the phosphor sample according to the example 8also had the orthorhombic crystal structure, and the value of the a-axiswas 9.808 Å, the value of the b-axis was 5.656 Å, the value of thec-axis was 5.068 Å, the crystal lattice volume was 281.14 Å³, and thesize of the crystallite (Dx) was 102.6 nm, e.g. not less than 50.0 nm.

From the aforementioned evaluation results, the lattice constant of eachcrystal lattice of the a-axis, b-axis, and c-axis in the phosphor sampleis increased, with the improvement of the emission characteristic of thephosphor sample, and simultaneously, the increase of the crystal latticevolume is observed. Then, the lattice constant is increased and thecrystal lattice volume is increased in proportion to the reduction ofthe amount of the oxygen contained in the phosphor sample, and when theamount of the oxygen in the phosphor sample is reduced, the crystallattice volume is increased. Details are unknown, regarding the cause ofthe increase of the crystal lattice volume in association with thereduction of the amount of the oxygen in the phosphor sample. It isconsidered that the oxygen enters into CaAlSiN₃ lattice of the phosphorsample, thereby replacing the nitrogen in the lattice with the oxygen,or the lattice volume of the impurity phase, in which the oxygen ismixed in, is small. Therefore, it is estimated that when the ratio ofthe impurity phase is increased, the lattice volume is relativelydecreased. Accordingly, when the phase has increased lattice constantand lattice volume and a large crystallite, it is estimated that furtherpure phase having an excellent emission characteristic is generated.From the viewpoint of the emission characteristic, in order to obtainthe phosphor having the emission peak wavelength of 650 nm or more,preferably the amount of the oxygen contained as the impurity is 3.0 wt% or less, and the lattice constant of each crystal lattice is a=9.75 Åor more, b=5.64 Å or more, and c=5.05 Å or more, and the volume of thecrystal lattice is 275.0 Å³ or more, and further preferably a=9.80 Å ormore, b=5.65 Å or more, c=5.06 Å or more, and the volume of the crystallattice is 280.5 Å³ or more. Incidentally, when compared with thecrystal structure of CaAlSiN₃ described in 39-0747 of the JCPDS card,the lattice constant and the volume of the phosphor sample according tothis example is more dramatically increased.

Note that the phosphor sample shown in the example 8 exhibits thehighest emission characteristic.

3.) Regarding the Powder Characteristic

The phosphor powder obtained in the example 1 and the examples 7 and 8has a smaller average particle size (D50), compared with the phosphorparticle obtained in the examples 3 and 4. However, when the particlesize is measured by the SEM observation, a primary particle size of theexamples 3 and 4 is 3 to 4 μm, which is the same size as seen in theexamples 7 and 8. However, a huge particle of more than 20 μm existed atonly a partial region, and sintering of the primary particles was alsoobserved. As a result of the measurement of a particle size by a laserdiffraction scattering method, it was found that no huge particleexisted in the examples 1, 7, and 8, and the particle with significantlyuniform diameter was generated.

As described above, when the crystal lattice volume and the size of thecrystallite of the crystal contained in the phosphor sample becomelarge, or the amount of the oxygen in the crystal is reduced, thephosphor particle with uniform particle diameter is easily generatedafter phosphor generation, and preferably particle characteristic andpulverizing characteristic are thereby improved. For example, apreferable result could be obtained, such that the particle of thephosphor sample obtained in the examples 7 and 8 showed 1.0 or less of acoefficient of variation (standard deviation/average size) of adistribution of the particle size after pulverizing, thereby providing asignificantly sharp distribution of the particle size.

A absolute density measurement was performed in each phosphor sample,and it was found that the phosphor with excellent emissioncharacteristic showed the value near 3.240 g/cc. For measuring theabsolute density, Ultrapycnometer 1000 by QUANTACHROME INC. was used.When the absolute density was measured for the phosphors of the examples3 and 4 for comparison, it was found that the absolute density had thetendency of reduction from 3.240 g/cc. This is because the impurityphase having a lower absolute density different from CaAlSiN₃:Eu wasgenerated, and as a result, an overall absolute specific gravity is alsolightened. As described above, it was found that the absolute density ofthe phosphor was in the range of 3.240 g/cc±3%, and preferably in therange of 3.240 g/cc±1%.

4.) Regarding Durability

An evaluation of durability of the phosphor was performed for eachphosphor sample according to the examples 1 to 4, 7 and 8.

The evaluation method of the durability of the phosphor was performed insuch a manner that each sample was subjected to heat treatment 300° C.in an atmospheric air for 30 minutes, and a difference in intensity ofthe emission spectrum when the phosphor was irradiated withmonochromatic light with the wavelength of 460 nm was evaluated, for thesample before the heat treatment and after the heat treatment.Specifically, the relative intensity of the maximum peak in the emissionspectrum of the sample before the heat treatment was defined as 100%,and next the relative intensity of the maximum peak in the emissionspectrum of the sample after the heat treatment was obtained bypercentage, and lowering rate of the relative intensity of the maximumpeak accompanying the heat treatment was obtained by the negative value.The evaluation result is shown in table 1. Then, it was found that thedurability against the heat treatment was improved as the lattice volumeof the crystal contained in the phosphor sample was increased, wasimproved as the oxygen concentration in the crystal was lowered, and wasimproved when the absolute density of the sample was closer to 3.240g/cc. The reason is considered to be that the crystallites in thephosphor sample are more regularly arrayed, thus preventing the invasionof the oxygen in the crystal, whereby the deterioration of the emissioncharacteristic can be suppressed.

Comparative Example 1

Ca₂Si₅N₈:Eu phosphor was prepared based on the aforementioned patentdocuments 4 and 5, and the X-ray diffraction pattern was measured. Themeasurement result is shown in FIG. 5. Then, the X-ray diffraction peakobtained in FIG. 5 and the structure analysis result in the documentdescribed in the patent document 4 (Schlieper and Schlick:Nitridosilicate I, Hochtemperatursynthese and Kristallstruktur vonCa2Si5N8, Z. anorg.allg.Che. 621, (1995), p. 1037) were compared. As aresult, it was confirmed that the aforementioned phosphor was theCa₂Si₅N₈:Eu phosphor described in the patent documents 4 and 5. Thecrystal system of the phosphor is a monoclinic system, however iscompletely different in structure from the phosphor according to thepresent invention.

Comparative Example 2

An α-sialon phosphor was prepared based on the aforementioned patentdocument 3, and the X-ray diffraction pattern was measured. Here, theα-sialon is oxide nitride ceramics with intermediate composition ofnitride and oxide, composed of 4 elements such as silicon, aluminum,oxygen, and nitrogen, and Al is substituted for the Si position, and Ois substituted for the N position of α-Si₃N₄, to form a solid solution,having a framework comprising a tetrahedron structure of (Si, Al) (O,N), and further having the structure wherein metal M (M:Mg, Ca, andlantanide metal except Y, La, and Ce, satisfying 0<x≦2) can be dissolveddifferently from β-sialon. As a result, the X-ray diffraction peak ofthe α-sialon phosphor shows the diffraction pattern similar to that ofthe X-ray diffraction peak of the α-Si₃N₄. The measurement result isshown in FIG. 6.

The X-ray diffraction peak shown in FIG. 6 has a similar pattern to thatof the α-Si₃N₄. Then, the pattern thus obtained was further comparedwith the diffraction pattern of the sialon reported in the JCPDS. As aresult, the X-ray diffraction peaks of both patterns coincide with eachother, and it was confirmed that the phosphor according to theconventional art shown in FIG. 6 was the α-sialon phosphor described inthe patent document 3. In addition, the crystal system of the α-sialonwas a hexagonal system, which was a completely different structure fromthe phosphor according to the present invention.

Comparative Example 3

In the same way as the example 7 excepting that the ventilation of thenitrogen in the firing furnace was stopped, the phosphor samplecontaining the product phase expressed by the composition formulaCa_(0.985)AlSiN₃:Eu_(0.0150) was manufactured. The emissioncharacteristic, the powder characteristic, and other characteristics ofthe phosphor sample thus obtained are shown in table 1. Then, in thesame way as the examples 1 to 8, the crystal structure analysis of thephosphor was performed. As a result, it was found that the unit latticeof the phosphor according to the comparative example 3 was that thea-axis was 9.790 Å, the b-axis was 5.641 Å, the c-axis was 5.058 Å, thecrystal lattice volume was 279.3 Å3, and the size (Dx) of thecrystallite was 87.6 nm.

Further, it was found that the emission intensity of the phosphor sampleaccording to the comparative example 3 was almost 20% lower than that ofthe phosphor sample according to the example 7. In addition, it wasfound that the durability against the heat treatment was deteriorated.This is because by stopping the ventilation of the nitrogen in thefiring furnace, the oxygen during firing was not sufficiently removed,and the amount of the oxygen was increased in a generated product,whereby both of the crystal lattice volume and the size of thecrystallite were reduced.

1. A phosphor comprising: a product phase expressed by a compositionformula MADOoNn:Z, where element M is at least one or more kind ofelement having bivalent valency, element A is at least one or more kindof element having tervalent valency, element D is at least one or morekind of element selected from the elements having tetravalent valency, Ois oxygen, N is nitrogen, and element Z is at least one more kind ofelement selected from rare earth elements or transitional metal elementssatisfying n=3-2/30, o+n>8/3, and showing a diffraction peak withrelative intensity of 10% or more in the Bragg angle (2θ) range from36.5° to 37.5° and from 41.9° to 42.9° of the X-ray diffraction pattern,when the relative intensity of the diffraction peak having a highestintensity in a powder X-ray diffraction pattern by CoKα ray is definedas 100%, wherein a crystal lattice volume of the product phase is 280.5Å³ or more.
 2. The phosphor according to claim 1, wherein a crystallitesize of the product phase is 90 nm or more.
 3. The phosphor according toclaim 1, wherein the element M is one or more kind of element havingbivalent valency, indispensably including Ca; the element A is one ormore kind of element having tervalent valency, indispensably includingAl; and the element D is one or more kind of element having tetravalentvalency, indispensably including Si.
 4. A light source manufacturedusing the phosphor according to claim 1.